Centrifugal chiller and centrifugal chiller operation method

ABSTRACT

A centrifugal chiller includes a first expansion unit (23) that expands refrigerant that has been compressed and condensed, and an evaporation unit (41) that evaporates the expanded refrigerant and supplies the evaporated refrigerant to a compression unit (15). The first expansion unit (23) has an orifice (20) through which refrigerant condensed by a condensation unit (17) passes, and a flow rate regulation valve (22) that can regulate the amount of refrigerant condensed by the condensation unit (17) flowing through and that is connected in parallel with the orifice (20).

TECHNICAL FIELD

The present invention relates to a centrifugal chiller and a centrifugal chiller operation method.

Priority is claimed on Japanese Patent Application No. 2017-036285, filed Feb. 28, 2017, the content of which is incorporated herein by reference.

BACKGROUND ART

In general, a centrifugal chiller has a refrigeration cycle which includes a compressor (compression unit), a condenser (condensation unit), an evaporator (evaporation unit), and a pressure reduction mechanism (expansion unit) (refer to PTL 1).

In the centrifugal chiller configured as described above, a high-pressure gas refrigerant compressed according to a capacity control operation of the compressor is supplied to the condenser to be condensed and liquefied. Thereafter, a liquid refrigerant is expanded under reduced pressure using the pressure reduction mechanism (expansion unit) and is supplied to the evaporator, and the liquid refrigerant is evaporated by the evaporator and is returned to the compressor.

PTL 1 discloses that an orifice is used as a pressure reduction mechanism (expansion unit).

Citation List Patent Literature

[PTL 1] Japanese Unexamined Patent Application Publication No. 4-324065

SUMMARY OF INVENTION Technical Problem

Meanwhile, in a case of -a rated operation of a centrifugal chiller, flow characteristics of a refrigerant may be constant (since adjustment of an opening degree is unnecessary), and thus, there is no problem in the orifice disclosed in PTL 1.

However, in a case of a partial load operation of a turbo compressor, a flow coefficient deviates from an optimal value, and thus, the orifice is difficult to cope with the partial load operation.

In addition, in a case where the turbo compressor uses a pressure reduction mechanism (expansion unit) corresponding to the partial load operation, it is preferable to prevent a size of the centrifugal chiller from increasing.

Accordingly, an object of the present invention is to provide a centrifugal chiller and a centrifugal chiller operation method capable of suppressing a decrease in performance during a partial load operation while suppressing an increase in size.

Solution to Problem

In order to achieve the object, according to an aspect of the present invention, there is provided a centrifugal chiller including: a refrigeration cycle which includes a compression unit which compresses a refrigerant, a condensation unit which condenses the refrigerant compressed by the compression unit, an expansion unit which expands the refrigerant condensed by the condensation unit, and an evaporation unit which evaporates the refrigerant expanded by the expansion unit and supplies the expanded refrigerant to the compression unit, and through which the refrigerant circulates, in which the expansion unit includes an orifice through which the refrigerant condensed by the condensation unit passes, and a flow regulation valve which is connected in parallel to the orifice and adjusts a passing amount of the refrigerant condensed by the condensation unit.

According to the present invention, the expansion unit includes the orifice through which the refrigerant condensed by the condensation unit passes, and a flow regulation valve which is connected in parallel to the orifice and adjusts a passing amount of the refrigerant condensed by the condensation unit. Therefore, when a load factor is equal to or more than a partial load peak at which a coefficient of performance during a partial load operation is maximized, the refrigerant condensed by the condensation unit can pass through the orifice and the flow regulation valve, and when the load factor is less than the partial load peak, the flow regulation valve is fully closed, the refrigerant condensed by the condensation unit can pass through only the orifice. Accordingly, it is possible to suppress a decrease in performance during the partial load operation.

In addition, the orifice and the flow regulation valve are used together, and thus, it is possible to decrease a diameter of the flow regulation valve. Therefore, it is possible to decrease a size of the expansion unit, and thus, it is possible to suppress an increase in size of the centrifugal chiller.

In addition, in the centrifugal chiller according to the aspect of the present invention, the centrifugal chiller may further include a control device which is electrically connected to the flow regulation valve, the control device may cause the refrigerant condensed by the condensation unit to pass through the orifice and the flow regulation valve when the load factor is equal to or more than a partial load peak at which a coefficient of performance during a partial load operation is maximized, and the control device may fully close the flow regulation valve and may cause the refrigerant condensed by the condensation unit to pass through only the orifice when the load factor is less than the partial load peak.

The control device configured as described above makes it possible to suppress the decrease in performance during the partial load operation while suppressing the increase in size of the centrifugal chiller.

In addition, in the centrifugal chiller according to the aspect of the present invention, the centrifugal chiller may further include an inlet temperature detection unit which is electrically connected to the control device and detects a cooling water inlet temperature which is a temperature of cooling water introduced into the condensation unit, an outlet temperature detection unit which is electrically connected to the control device and detects a cooling water outlet temperature which is a temperature of the cooling water led out from an inside of the condensation unit, a flow meter which measures a flow rate of the cooling water, a first flow rate detector which is electrically connected to the control device and detects a first flow rate of the refrigerant flowing through the orifice, the refrigerant being a liquid, and a second flow rate detector which is electrically connected to the control device and detects a second flow rate of the cooling water flowing through the flow regulation valve, the cooling water being a liquid, in which based on the cooling water inlet temperature, the cooling water outlet temperature, the flow rate of the cooling water, and the load factor during an operation, the control device may regulate an opening degree of the flow regulation valve such that a sum of the first and second flow rates is a predetermined circulation flow rate.

In the way, the control device, which regulates the opening degree of the flow regulation valve such that the sum of the first and second flow rate is the predetermined circulation flow rate, based on the cooling water inlet temperature, the cooling water outlet temperature, the flow rate of the cooling water, and the load factor during an operation, makes it possible to suppress the decrease in the performance during the partial load operation.

In addition, in the centrifugal chiller according to the aspect of the present invention, the flow regulation valve may be an electric ball valve.

In this way, the electric ball valve is used as the flow regulation valve, and thus, it is possible to decrease a diameter of the electric ball valve. Accordingly, it is possible to suppress the increase in size of the flow regulation valve.

Moreover, in the centrifugal chiller according to the aspect of the present invention, the centrifugal chiller may further include an economizer which is disposed between the condensation unit and the evaporation unit, reduces a pressure of a portion of a high-temperature and high-pressure refrigerant compressed by the compression unit to an intermediate pressure, and returns the refrigerant whose pressure is reduced to the intermediate pressure to the compression unit, in which the expansion unit may be disposed between the condensation unit and the economizer and between the economizer and the evaporation unit.

The economizer configured as described above makes it possible to extract a large refrigeration capacity even with small power.

Moreover, in the centrifugal chiller according to the aspect of the present invention, the centrifugal chiller may further include a first line which connects an outlet of the condensation unit and an inlet of the economizer to each other, and a second line which connects an outlet of the economizer and an inlet of the evaporation unit to each other, in which one of the orifice and the flow regulation valve may be provided in each of the first and second lines, and a bypass line which bypasses the one may be provided in each of the first and second lines and the other of the orifice and the flow regulation valve may be provided in the bypass line.

According to this configuration, the refrigerant can flow to both the orifice and the flow regulation valve or the refrigerant can flow to only the orifice.

In addition, in the centrifugal chiller according to the aspect of the present invention, the refrigerant may be a low-pressure refrigerant whose pressure in normal use is less than 0.2 MPa.

In general, the low-pressure refrigerant has a large specific volume as compared to a high-pressure refrigerant which is a subject to a regulation of a high pressure gas. Therefore, for example, if the orifice is not provided and only the flow regulation valve is provided in the centrifugal chiller, the size of the flow regulation valve increases.

However, the orifice and the flow regulation valve are used together, and thus, it is possible to suppress an increase in size of the flow regulation valve.

In order to achieve the object, according to another aspect of the present invention, there is provided an operation method of a centrifugal chiller including a refrigeration cycle which includes a compression unit which compresses a refrigerant, a condensation unit which condenses the refrigerant compressed by the compression unit, an expansion unit which expands the refrigerant condensed by the condensation unit, and an evaporation unit which evaporates the refrigerant expanded by the expansion unit and supplies the expanded refrigerant to the compression unit, and through which the refrigerant circulates, the expansion unit including an orifice through which the refrigerant condensed by the condensation unit passes, and a flow regulation valve which is connected in parallel to the orifice and adjusts a passing amount of the refrigerant condensed by the condensation unit, the operation method including: allowing the refrigerant condensed by the condensation unit to pass through the orifice and the flow regulation valve when a load factor is equal to or more than a partial load peak at which a coefficient of performance during a partial load operation is maximized; and fully closing the flow regulation valve and allowing the refrigerant condensed by the condensation unit to pass through only the orifice when the load factor is less than the partial load peak.

In this way, when the load factor is equal to or more than a partial load peak at which a coefficient of performance during a partial load operation is maximized, the refrigerant condensed by the condensation unit passes through the orifice and the flow regulation valve, and when the load factor is less than the partial load peak, the flow regulation valve is fully closed, the refrigerant condensed by the condensation unit passes through only the orifice. Accordingly, it is possible to suppress a decrease in performance during the partial load operation while suppressing an increase in size of the centrifugal chiller.

In addition, in the operation method of a centrifugal chiller according to another aspect of the present invention, the operation method may further include based on a cooling water inlet temperature which is a temperature of cooling water introduced into the condensation unit, a cooling water outlet temperature which is a temperature of the cooling water led out from an inside of the condensation unit, a flow rate of the cooling water, a first flow rate of the refrigerant flowing through the orifice, the refrigerant being a liquid, a second flow rate of the cooling water flowing through the flow regulation valve, the cooling water being a liquid, and the load factor during an operation, regulating an opening degree of the flow regulation valve such that a sum of the first and second flow rates is a predetermined circulation flow rate.

According to this operation, it is possible to suppress the decrease in performance during the partial load operation

In addition, in the operation method of a centrifugal chiller according to another aspect of the present invention, the refrigerant may be a low-pressure refrigerant whose pressure in normal use is less than 0.2 MPa.

In general, the low-pressure refrigerant has a large specific volume as compared to the high-pressure refrigerant which is a subject to a regulation of the high pressure gas. Therefore, for example, if the orifice is not provided and only the flow regulation valve is provided in the centrifugal chiller, the size of the flow regulation valve increases.

However, the orifice and the flow regulation valve are used together, and thus, it is possible to suppress an increase in size of the flow regulation valve.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to suppress a decrease in performance during a partial load operation while suppressing an increase in size of a centrifugal chiller.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram showing a schematic configuration of a centrifugal chiller according to an embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a load factor (%) of the centrifugal chiller, a coefficient of performance (COP), and a temperature of a cooling water.

FIG. 3 is a functional block diagram of a control device of FIG. 1.

FIG. 4 is a graph showing a relationship between a flow rate of a refrigerant passing through an orifice each cooling inlet temperature, a flow rate of the refrigerant passing through a flow regulation valve at each cooling inlet temperature, the load factor of the centrifugal chiller, and a temperature of an opening degree of the flow regulation valve.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment to which the present invention is applied will be described in details with reference to the drawings.

Embodiment

A centrifugal chiller 10 of the present embodiment will be described with reference to FIG. 1. In FIG. 1, as an example, a case where cooling water generated by an evaporation unit 41 is used in an external load 6 will be described as an example. In FIG. 1, for convenience of explanation, the external load 6 which is not a component of the centrifugal chiller 10 is shown.

The centrifugal chiller 10 has a refrigeration cycle 9, a cooling tower 11, a cooling water circulation line 12, a chilled water circulation line 13, and a control device 14.

The refrigeration cycle 9 has a compression unit 15, lines 16, 32, and 43, a condensation unit 17, an inlet temperature detection unit 18A, an outlet temperature detection unit 18B, a flow meter 18C, a first line 19, bypass lines 21 and 36, a first expansion unit 23, first flow rate detectors 26 and 39, second flow rate detectors 29 and 40, an economizer 31, a second line 34, a second expansion unit 38, and an evaporation unit 41.

The compression unit 15 is a centrifugal two-stage compressor and is electrically connected to the control device 14.

The compression unit 15 has a rotary shaft (not shown), a low stage-side compression unit 51, a high stage-side compression unit 52, a motor 53, inlets 15A and 15B, and an outlet 15C.

The rotary shaft is configured to be rotatable by the motor 53. The low stage-side compression unit 51 and the high stage-side compression unit 52 are provided in the rotary shaft.

An inlet side of the low stage-side compression unit is connected to the other end of the line 43 via the inlet 15A. A refrigerant gas led out from the evaporation unit 41 is introduced into the inlet side of the low stage-side compression unit 51 via the line 43. An outlet side of the low stage-side compression unit 51 is connected to an inlet side of the high stage-side compression unit 52. The refrigerant gas compressed by the low stage-side compression unit 51 is supplied to the inlet side of the high stage-side compression unit 52.

A portion between the outlet side of the low stage-side compression unit 51 and the inlet side of the high stage-side compression unit 52 is connected to the other end of the line 32 via the inlet 15B. Accordingly, an intermediate-pressure refrigerant gas generated by the economizer 31 is injected to the portion between the low stage-side compression unit 51 and the high stage-side compression unit 52 via the line 32. An outlet side of the high stage-side compression unit 52 is connected to one end of the line 16.

The compression unit 15 configured as described above compresses the refrigerant gas in a two-step compression manner to generate a high-temperature and high-pressure gas refrigerant, and leads the high-temperature and high-pressure gas refrigerant to the line 16.

The other end of the line 16 is connected to an inlet 17A of the condensation unit 17. The high-temperature and high-pressure gas refrigerant generated by the compression unit 15 is supplied to the condensation unit 17 through the line 16.

The condensation unit 17 has the inlet 17A and an outlet 17B. The high-temperature and high-pressure gas refrigerant is introduced into the inlet 17A via the line 16. The outlet 17B is connected to one end of the first line 19.

A portion of the cooling water circulation line 12 through which cooling water cooled by the cooling tower 11 circulates is disposed in the condensation unit 17.

Accordingly, the cooling water which is supplied into the condensation unit 17 to cool the gas refrigerant and whose temperature increases is recovered to the cooling tower 11 via the cooling water circulation line 12, is cooled again, and thereafter, is supplied into the condensation unit 17.

In the condensation unit 17 configured as described above, heat exchange is performed between the high-temperature and high-pressure gas refrigerant and the cooling water, the gas refrigerant is condensed, and thus, a liquid refrigerant is generated. The generated liquid refrigerant is led to the first line 19. For example, a condenser can be used as the condensation unit 17.

The inlet temperature detection unit 18A is provided in the cooling water circulation line 12 through which the cooling water circulates between the cooling tower 11 and the condensation unit 17. The inlet temperature detection unit 18A is disposed at a position at which the inlet temperature detection unit 18A can detect a temperature (hereinafter, referred to as a “cooling water inlet temperature”) of the cooling water which is cooled by the cooling tower 11 and is introduced into the condensation unit 17.

The inlet temperature detection unit 18A is electrically connected to the control device 14. A temperature detection unit 18 transmits information on the detected cooling water inlet temperature to the control device 14.

The outlet temperature detection unit 18B is provided in the cooling water circulation line 12. The outlet temperature detection unit 18B is disposed at a position at which the outlet temperature detection unit 18B can detect a temperature (hereinafter, referred to a “cooling water outlet temperature”) of the cooling water led from the condensation unit 17.

The outlet temperature detection unit 18B is electrically connected to the control device 14. The outlet temperature detection unit 18B transmits information on the detected cooling water outlet temperature to the control device 14.

The flow meter 18C is provided in the cooling water circulation line 12. The flow meter 18C measures a flow rate of the cooling water supplied to the condensation unit 17. The flow meter 18C is electrically connected to the control device 14. The flow meter 18C transmits information on the measured flow rate of the cooling water to the control device 14.

The other end of the first line 19 is connected to an inlet 31A of the economizer 31. The liquid refrigerant which is condensed by the condensation unit 17 and whose pressure is reduced to an intermediate pressure is supplied to the inlet 31A of the economizer 31 through the first line 19.

An orifice 20 constituting the first expansion unit 23 is provided in the first line 19.

During a rated operation and a partial load operation, the liquid refrigerant generated by the condensation unit 17 passes through the orifice 20. A diameter of the orifice 20 is set so as to exert desired performance.

The bypass line 21 branches off from a portion of the first line 19 positioned between the outlet 17B and the orifice 20. A distal end of the bypass line 21 is connected to the first line 19 such that the bypass lines 21 bypasses the orifice 20.

The first expansion unit 23 functions as a high-pressure expansion unit. The first expansion unit 23 has the above-described orifice 20 and a flow regulation valve 22.

The flow regulation valve 22 is provided in the bypass line 21. Accordingly, the flow regulation valve 22 is connected in parallel to the orifice 20 and is configured to allow a passage of the liquid refrigerant generated by the condensation unit 17.

The flow regulation valve 22 is electrically connected to the control device 14. Opening and closing (opening degree) of the flow regulation valve 22 are controlled by the control device 14. Accordingly, the flow regulation valve 22 adjusts a passing amount of the refrigerant condensed by the condensation unit 17.

Here, with reference to FIG. 2, a partial load peak D_(T) will be described, in which a coefficient of performance (COP) during the partial load operation is maximized. In FIG. 2, a load factor 100% becomes the rated operation.

In curves A to E shown in FIG. 2, temperatures of the cooling water are different from each other. The temperature of the cooling water of the curve A is highest, and the temperature of the cooling water of the curve E is lowest. In the order of the curve A, the curve B, the curve C, the curve D, and the curve E, the temperature of the cooling water decreases. In a case where the load factors are the same as each other, as the temperature of the cooling water decreases, the coefficient of performance (COP) increases.

In the case of FIG. 2, during the partial load operation, the partial load peak D_(T) at which the coefficient of performance (COP) is maximized is a peak position of the curve D when the load factor is X % (for example, a predetermined value of 20% or more to 30% or less).

When the load factor is (the load factor is X % or more and less than 100%) equal to or more than the partial load peak D_(T) at which the coefficient of performance (COP) during the partial load operation is maximized, the refrigerant condensed by the condensation unit 17 passes through the orifice 20 and the flow regulation valve 22 configured as described above. In this case, the opening degree of the flow regulation valve 22 is regulated by the control device 14. In addition, the adjustment of the opening degree of the flow regulation valve 22 performed by the control device 14 will be described later.

Meanwhile, when the load factor is less than the partial load peak D_(T) (the load factor is less than X %), the flow regulation valve 22 is fully closed, the refrigerant condensed by the condensation unit 17 passes through only the orifice 20.

The first expansion unit 23 configured as described above reduces the pressure of the condensed liquid refrigerant to an intermediate pressure.

The above-described first expansion unit 23 is provided, and thus, when the load factor is equal to or more than the partial load peak D_(T) at which the coefficient of performance (COP) during the partial load operation is maximized, the refrigerant condensed by the condensation unit 17 can pass through the orifice 20 and the flow regulation valve 22, and when the load factor is less than the partial load peak D_(T), the flow regulation valve 22 is fully closed, the refrigerant condensed by the condensation unit 17 can pass through only the orifice 20. Accordingly, it is possible to suppress a decrease in performance of the centrifugal chiller 10 during the partial load operation.

In addition, the orifice 20 and the flow regulation valve 22 are used together, it is possible to decrease a diameter of the flow regulation valve 22, and thus, it is possible to decrease a size of the first expansion unit 23. Accordingly, it is possible to suppress an increase in size of the centrifugal chiller 10.

In addition, for example, an electric ball valve may be used as the flow regulation valve 22. In this way, the electric ball valve is used as the flow regulation valve 22, and thus, it is possible to decrease the diameter of the electric ball valve, and it is possible to suppress the increase in size of the flow regulation valve 22.

The first flow rate detector 26 is provided in a portion of the first line 19 positioned between a connection position 21A of the bypass line 21 and the orifice 20. The first flow rate detector 26 is electrically connected to the control device 14.

The first flow rate detector 26 detects a flow rate (hereinafter, referred to as a “first flow rate”) of a liquid refrigerant flowing through the orifice 20 and transmits information of the detected first flow rate to the control device 14.

The second flow rate detector 29 is provided in a portion of the bypass line 21 positioned between the connection position 21A of the bypass line 21 and the flow regulation valve 22. The second flow rate detector 29 is electrically connected to the control device 14.

The second flow rate detector 29 detects a second flow rate of a liquid refrigerant flowing through the flow regulation valve 22 and transmits information on the detected second flow rate to the control device 14.

The economizer 31 is a gas-liquid separator which functions as an economizer. The economizer 31 separates the liquid refrigerant whose pressure is reduced to the intermediate pressure into the liquid refrigerant and the gas refrigerant.

The economizer 31 has the inlet 31A and outlets 31B and 31C. The inlet 31A is connected to the other end of the first line 19. The liquid refrigerant whose pressure is reduced to the intermediate pressure by the first expansion unit 23 is introduced into the inlet 31A.

The outlet 31B is connected to one end of the second line 34. The outlet 31B leads the liquid refrigerant to the second line 34. The outlet 31C is connected to one end of the line 32. The outlet 31C leads the gas refrigerant to the line 32.

The other end of the line 32 is connected to the inlet side of the low stage-side compression unit 51 via the inlet 15A. The line 32 supplies the gas refrigerant to the low stage-side compression unit 51.

The other end of the second line 34 is connected to an inlet 41A of the evaporation unit 41. The liquid refrigerant is supplied to the inlet 41A of the evaporation unit 41 through the second line 34.

The orifice 35 constituting the second expansion unit 38 is provided in the second line 34.

During the rated operation and the partial load operation, the liquid refrigerant led out from the economizer 31 passes through the orifice 35. A diameter of the orifice 35 is set so as to exert desired performance.

The bypass line 36 branches off from a portion of the second line 34 positioned between the orifice 35 and the inlet 41A of the evaporation unit 41. A distal end of the bypass line 36 is connected to the second line 34 such that the bypass lines 36 bypasses the orifice 35.

The second expansion unit 38 functions as a low-pressure expansion unit. The second expansion unit 38 has the above-described orifice 35 and a flow regulation valve 37.

The flow regulation valve 37 is provided in the bypass line 36. Accordingly, the flow regulation valve 37 is connected in parallel to the orifice 35, and the liquid refrigerant which is subjected to the gas-liquid separation by the economizer 31 can pass through the flow regulation valve 37.

The flow regulation valve 37 is electrically connected to the control device 14. Opening and closing (opening degree) of the flow regulation valve 37 are controlled by the control device 14. Accordingly, the flow regulation valve 37 adjusts a passing amount of the liquid refrigerant which is subjected to the gas-liquid separation by the economizer 31.

For example, as the flow regulation valve 37, a flow regulation valve (for example, electric ball valve) similar to the above-described flow regulation valve 22 can be used.

When the load factor is (the load factor is X % or more and less than 100%) equal to or more than the partial load peak D_(T) at which the coefficient of performance (COP) during the partial load operation is maximized, the refrigerant condensed by the condensation unit 17 passes through the orifice 35 and the flow regulation valve 37 configured as described above. In this case, the opening degree of the flow regulation valve 37 is regulated by the control device 14.

Meanwhile, when the load factor is less than the partial load peak D_(T) (the load factor is less than X %), the flow regulation valve 37 is fully closed, the liquid refrigerant passes through only the orifice 35.

The second expansion unit 38 configured as described above decreases the condensed liquid refrigerant to a low pressure.

The first flow rate detector 39 is provided in a portion of the second line 34 positioned between a connection position 36A of the bypass line 36 and the orifice 35. The first flow rate detector 39 is electrically connected to the control device 14.

The first flow rate detector 39 detects the first flow rate of the liquid refrigerant flowing through the orifice 35 and transmits information on the detected first flow rate to the control device 14.

The second flow rate detector 40 is provided in a portion of the bypass line 36 positioned between the connection position 36A of the bypass line 36 and the flow regulation valve 37. The second flow rate detector 40 is electrically connected to the control device 14.

The second flow rate detector 40 detects the second flow rate of the liquid refrigerant flowing through the flow regulation valve 37 and transmits information on the detected second flow rate to the control device 14.

The evaporation unit 41 has the inlet 41A and an outlet 41B. The inlet 41A is connected to the other end of the second line 34. A low-pressure refrigerant whose pressure is reduced by the second expansion unit 38 is supplied to the inlet 41A via the second line 34. The outlet 41B is connected to one end of the line 43.

A portion of the chilled water circulation line 13 to which the chilled water circulating between the external load 6 and the evaporation unit 41 flows is disposed in the evaporation unit 41. Heat exchange is performed between the chilled water flowing through the chilled water circulation line 13 and the low-pressure refrigerant by the evaporation unit 41, and thus, the low-pressure refrigerant is evaporated and the gas refrigerant is generated.

The evaporation unit 41 supplies the generated gas refrigerant to the inlet 15A of the compression unit 15 via the line 43.

The cooling tower 11 cools the cooling water which passes through the condensation unit 17 and whose temperature increases. The cooled cooling water is supplied to the condensation unit 17 via the cooling water circulation line 12.

The cooling water circulation line 12 is connected to the cooling tower 11 and a portion of the cooling water circulation line 12 is accommodated in the condensation unit 17. The cooling water circulates through the cooling water circulation line 12 between the cooling tower 11 and the condensation unit 17.

The chilled water circulation line 13 is connected to the external load 6 (for example, air conditioner) and a portion of the chilled water circulation line 13 is disposed in the evaporation unit 41. The chilled water circulates through the chilled water circulation line 13 between the external load 6 and the evaporation unit 41.

The control device 14 will be described with reference to FIGS. 1, 3, and 4.

The control device 14 has a load factor acquisition unit 60, a compression unit controller 61, a map storage unit 62, a flow regulation valve opening degree acquisition unit 64, and a flow regulation valve controller 66.

The load factor acquisition unit 60 is electrically connected to the inlet temperature detection unit 18A, the outlet temperature detection unit 18B, the flow meter 18C, the compression unit 15, the compression unit controller 61, and the flow regulation valve opening degree acquisition unit 64. The load factor acquisition unit 60 acquires a load capacity based on the cooling water inlet temperature, the cooling water outlet temperature, and the flow rate of the cooling water transmitted from the inlet temperature detection unit 18A, the outlet temperature detection unit 18B, and the flow meter 18C, and acquires a load factor X (%) based on the acquired load capacity.

Specifically, the load factor X (%) is acquired based on the following Expression (1).

load factor X (%)={(load capacity at any time)/(load capacity during rated operation)}×100   (1)

The load factor acquisition unit 60 transmits the information on the acquired load factor X to the compression unit controller 61 and the flow regulation valve opening degree acquisition unit 64.

The compression unit controller 61 is electrically connected to the compression unit 15. The compression unit controller 61 performs a control to reduce an output of the compression unit 15 when the load factor X (%) decreases.

The map storage unit 62 is electrically connected to the flow regulation valve opening degree acquisition unit 64. Map data (graph data) acquired in the advance as shown in FIG. 4 is stored in the map storage unit 62.

Here, a graph of FIG. 4 will be described. In the graph of FIG. 4, a horizontal axis indicates the load factor (%) of the centrifugal chiller 10, one vertical axis indicates the flow rate (kg/min) of the refrigerant, and the other vertical axis indicates the opening degree (%) of the flow regulation valve.

In FIG. 4, a curve related to the first flow rate of the liquid refrigerant passing through the orifice 20 in a case where the cooling water inlet temperatures are different from each other, a curve related to the second flow rate of the liquid refrigerant passing through the flow regulation valve 22 in a case where the cooling water inlet temperatures are different from each other, and a circulation flow rate (straight line) for the liquid refrigerant are shown.

The straight line of the “circulation flow rate of the liquid refrigerant” shown in FIG. 4 indicates a total flow rate (the flow rate of the liquid refrigerant introduced into the inlet 31A) of the refrigerant and a predetermined circulation flow rate corresponding to the load factor.

The temperatures in parentheses indicate the cooling water inlet temperatures. For example, (17° C.) means that the cooling water inlet temperature is 17° C.

The flow regulation valve opening degree acquisition unit 64 is electrically connected to the inlet temperature detection unit 18A, the first flow rate detectors 26 and 39, the second flow rate detectors 29 and 40, and the flow regulation valve controller 66.

The cooling water inlet temperature and the first and second flow rates of the liquid refrigerant detected by the first flow rate detectors 26 and 39 and the second flow rate detectors 29 and 40 are input to the flow regulation valve opening degree acquisition unit 64.

In the flow regulation valve opening degree acquisition unit 64, the opening degree (%) of the flow regulation valve 22 is acquired based on the load factor X (%), the cooling water inlet temperature, the first and second flow rates of the liquid refrigerant detected by the first and second flow rate detectors 26 and 29, and the map data shown in FIG. 4.

Specifically, during the partial load operation, based on the first flow rate (Kg/min) of the liquid refrigerant (the refrigerant which is a liquid) passing through the first flow rate detector 26 corresponding to the cooling water inlet temperature, the second flow rate (Kg/min) of the liquid refrigerant (the refrigerant which is a liquid) passing through the second flow rate detector 29 corresponding to the cooling water inlet temperature, and the load factor X (%), the flow regulation valve opening degree acquisition unit 64 acquires the opening degree (%) of the flow regulation valve 22 which causes a total flow rate of the first flow rate (Kg/min) of the liquid refrigerant (the refrigerant which is a liquid) passing through the first flow rate detector 26 and the second flow rate (Kg/min) of the liquid refrigerant (the refrigerant which is a liquid) passing through the second flow rate detector 29 to be a predetermined circulation flow rate (in this case, W (Kg/min)).

The graph of the opening degree of the flow regulation valve 22 used at this time uses a graph in which the temperatures of the cooling water are the same as each other. In addition, the opening degree of the flow regulation valve 22 is an opening degree of the flow regulation valve 22 to be acquired at a position at which a dotted line which passes through the load factor X and is parallel to the vertical axis and the graph of the opening degree of the flow regulation valve 22 intersect each other.

Moreover, the opening degree of the flow regulation valve 37 constituting the second expansion unit 38 is acquired using the same method as that of the flow regulation valve 22 described above.

The flow regulation valve opening degree acquisition unit 64 transmits the acquired information on the opening degrees of the flow regulation valves 22 and 37 to the flow regulation valve controller 66.

The flow regulation valve controller 66 is electrically connected to the flow regulation valves 22 and 37. The flow regulation valve controller 66 controls the opening degrees of the flow regulation valves 22 and 37 based on the information on the opening degrees of the flow regulation valves 22 and 37 transmitted from the flow regulation valve opening degree acquisition unit 64, respectively.

In the centrifugal chiller 10 configured as described above, as the refrigerant circulating through the refrigeration cycle 9, a high-pressure refrigerant (for example, R134a) whose pressure in a normal use exceeds 0.2 MPa or a low-pressure refrigerant (for example, R1233zd) whose pressure in a normal use is less than 0.2 MPa can be used.

The low-pressure refrigerant has a large specific volume as compared to the high-pressure refrigerant which is a subject to a regulation of a high pressure gas. Therefore, for example, if orifices 20 and 35 are not provided and only the flow regulation valves 22 and 37 are provided in the centrifugal chiller 10, the sizes of the flow regulation valves 22 and 37 increase.

However, in the above-described first and second expansion units 23 and 38, the orifices 20 and 35 and the flow regulation valves 22 and 37 are used together, and thus, it is possible to suppress the increase in size of each of the flow regulation valves 22 and 37.

According to the centrifugal chiller 10 of the present embodiment, the centrifugal chiller 10 has the first expansion unit 23 including the orifice 20 through which the refrigerant condensed by the condensation unit 17 passes and the flow regulation valve 22 which is connected in parallel to the orifice 20 and can adjust the passing amount of the refrigerant condensed by the condensation unit 17. Accordingly, when the load factor is equal to or more than the partial load peak D_(T) at which the coefficient of performance during the partial load operation is maximized, the refrigerant condensed by the condensation unit 17 can pass through the orifice 20 and the flow regulation valve 22, and when the load factor is less than the partial load peak D_(T), the flow regulation valve 22 is fully closed, and the refrigerant condensed by the condensation unit 17 can pass through only the orifice 20. Therefore, it is possible to suppress a decrease in performance during the partial load operation.

In addition, the orifice 20 and the flow regulation valve 22 are used together, and thus, it is possible to decrease the diameter of the flow regulation valve 22, and it is possible to reduce the size of the first expansion unit 23. Accordingly, it is possible to prevent the size of the centrifugal chiller 10 from increasing.

In addition, the second expansion unit 38 disposed between the economizer 31 and the evaporation unit 41 can also obtain the same effect as that of the first expansion unit 23.

Here, an operation method of the centrifugal chiller 10 shown in FIG. 1 will be briefly described.

In the centrifugal chiller 10, as described above, when the load factor is equal to or more than the partial load peak D_(T) at which the coefficient of performance (COP) during the partial load operation is maximized, the refrigerant condensed by the condensation unit 17 can pass through the orifice 20 and the flow regulation valve 22, and when the load factor is less than the partial load peak D_(T), the flow regulation valve 22 is fully closed, and the refrigerant condensed by the condensation unit 17 can pass through only the orifice 20.

The low-pressure liquid refrigerant is supplied to the evaporation unit 41 via the second expansion unit 38 configured similarly to the first expansion unit 23.

By performing this operation, it is possible to decrease the diameter of each of the flow regulation valves 22 and 37 constituting the first and second expansion units 23 and 38, and thus, it is possible to suppress the decrease in performance during the partial load operation while suppressing the increase in the size of the centrifugal chiller 10.

In addition, based on the cooling water inlet temperature which is the temperature of the cooling water introduced into the condensation unit 17, the cooling water outlet temperature which is the temperature of the cooling water led out from the inside of the condensation unit 17, the flow rate of the cooling water, the first flow rate of the liquid refrigerant flowing through the orifice 20, the second flow rate of the liquid cooling water flowing through the flow regulation valve 22, and the load factor during the operation, the opening degree of the flow regulation valve 22 may be regulated such that a sum of the first and second flow rate is a predetermined circulation flow rate.

By performing this operation, it is possible to suppress the decrease in the performance during the partial load operation.

In addition, it is possible to decrease the diameter of each of the flow regulation valves 22 and 37 even in a case where the low-pressure refrigerant (for example, R1233zd) whose pressure in normal use is less than 0.2 MPa is used, and thus, it is possible to suppress the increase in the size of the centrifugal chiller 10.

Hereinbefore, the preferred embodiments of the present invention are described in detail. However, the present invention is not limited to the specific embodiment, and various modifications and changes may be made within the scope of the present invention described in claims.

Moreover, in the present embodiment, as shown in FIG. 1, the case where the chilled water having the temperature lower than that of the cooling water is used in the external load 6 is described as an example. However, the external load 6 may use the cooling water which flows through the condensation unit 17 or flows through the cooling water circulation line 12. That is, the centrifugal chiller 10 shown in FIG. 1 may be used as a heat pump.

Moreover, in the present embodiment, the case where the economizer 31 is provided is described as an example. The economizer 31 may be provided as needed, and is not an essential configuration.

In addition, in a case where the economizer 31 is not provided, the first line 19 may be connected to the other end and the inlet 41A. Accordingly, in this case, the second line 34, the bypass line 36, the second expansion unit 38, the first flow rate detector 39, and the second flow rate detector 40 are not required.

INDUSTRIAL APPLICABILITY

The present invention can be applied to a centrifugal chiller and a centrifugal chiller operation method.

REFERENCE SIGNS LIST

6: external load

9: refrigeration cycle

10: centrifugal chiller

11: cooling tower

12: cooling water circulation line

13: chilled water circulation line

14: control device

15: compression unit

15A, 15B, 17A, 31A, 41A: inlet

15C, 17B, 31B, 31C, 41B: outlet

16, 32, 43: line

17: condensation unit

18A: inlet temperature detection unit

18B: outlet temperature detection unit

18C: flow meter

19: first line

20, 35: orifice

21, 36: bypass line

21A, 36A: connection position

22, 37: flow regulation valve

23: first expansion unit

26, 39: first flow rate detector

29, 40: second flow rate detector

31: economizer

34: second line

38: second expansion unit

41: evaporation unit

51: low stage-side compression unit

52: high stage-side compression unit

53: motor

60: load factor acquisition unit

61: compression unit controller

62: map storage unit

64: flow regulation valve opening degree acquisition unit

66: flow regulation valve controller

A to E: curve

D_(T): partial load peak 

1-10. (canceled)
 11. A centrifugal chiller comprising: a refrigeration cycle which includes a compression unit which compresses a refrigerant, a condensation unit which condenses the refrigerant compressed by the compression unit, an expansion unit which expands the refrigerant condensed by the condensation unit, and an evaporation unit which evaporates the refrigerant expanded by the expansion unit and supplies the expanded refrigerant to the compression unit, and through which the refrigerant circulates, wherein the expansion unit includes an orifice through which the refrigerant condensed by the condensation unit passes, and a flow regulation valve which is connected in parallel to the orifice and adjusts a passing amount of the refrigerant condensed by the condensation unit, and wherein the centrifugal chiller further comprises a control device which is electrically connected to the flow regulation valve, wherein the control device causes the refrigerant condensed by the condensation unit to pass through the orifice and the flow regulation valve when a load factor is equal to or more than a partial load peak at which a coefficient of performance during a partial load operation is maximized, and the control device fully closes the flow regulation valve and causes the refrigerant condensed by the condensation unit to pass through only the orifice when the load factor is less than the partial load peak.
 12. The centrifugal chiller according to claim 11, further comprising: an inlet temperature detection unit which is electrically connected to the control device and detects a cooling water inlet temperature which is a temperature of cooling water introduced into the condensation unit; an outlet temperature detection unit which is electrically connected to the control device and detects a cooling water outlet temperature which is a temperature of the cooling water led out from an inside of the condensation unit; a flow meter which measures a flow rate of the cooling water; a first flow rate detector which is electrically connected to the control device and detects a first flow rate of the refrigerant flowing through the orifice, the refrigerant being a liquid; and a second flow rate detector which is electrically connected to the control device and detects a second flow rate of the cooling water flowing through the flow regulation valve, the cooling water being a liquid, wherein based on the cooling water inlet temperature, the cooling water outlet temperature, the flow rate of the cooling water, and the load factor during an operation, the control device regulates an opening degree of the flow regulation valve such that a sum of the first and second flow rates is a predetermined circulation flow rate.
 13. The centrifugal chiller according to claim 11, wherein the flow regulation valve is an electric ball valve.
 14. The centrifugal chiller according to claim 11, further comprising: an economizer which is disposed between the condensation unit and the evaporation unit, reduces a pressure of a portion of a high-temperature and high-pressure refrigerant compressed by the compression unit to an intermediate pressure, and returns the refrigerant whose pressure is reduced to the intermediate pressure to the compression unit, wherein the expansion unit is disposed between the condensation unit and the economizer and between the economizer and the evaporation unit.
 15. The centrifugal chiller according to claim 14, further comprising: a first line which connects an outlet of the condensation unit and an inlet of the economizer to each other; and a second line which connects an outlet of the economizer and an inlet of the evaporation unit to each other, wherein one of the orifice and the flow regulation valve is provided in each of the first and second lines, and wherein a bypass line which bypasses the one is provided in each of the first and second lines and the other of the orifice and the flow regulation valve is provided in the bypass line.
 16. The centrifugal chiller according to claim 11, wherein the refrigerant is a low-pressure refrigerant whose pressure in normal use is less than 0.2 MPa.
 17. An operation method of a centrifugal chiller including a refrigeration cycle which includes a compression unit which compresses a refrigerant, a condensation unit which condenses the refrigerant compressed by the compression unit, an expansion unit which expands the refrigerant condensed by the condensation unit, and an evaporation unit which evaporates the refrigerant expanded by the expansion unit and supplies the expanded refrigerant to the compression unit, and through which the refrigerant circulates, the expansion unit including an orifice through which the refrigerant condensed by the condensation unit passes, and a flow regulation valve which is connected in parallel to the orifice and adjusts a passing amount of the refrigerant condensed by the condensation unit, the operation method comprising: allowing the refrigerant condensed by the condensation unit to pass through the orifice and the flow regulation valve when a load factor is equal to or more than a partial load peak at which a coefficient of performance during a partial load operation is maximized, and fully closing the flow regulation valve and allowing the refrigerant condensed by the condensation unit to pass through only the orifice when the load factor is less than the partial load peak.
 18. The operation method of a centrifugal chiller according to claim 17, further comprising: based on a cooling water inlet temperature which is a temperature of cooling water introduced into the condensation unit, a cooling water outlet temperature which is a temperature of the cooling water led out from an inside of the condensation unit, a flow rate of the cooling water, a first flow rate of the refrigerant flowing through the orifice, the refrigerant being a liquid, a second flow rate of the cooling water flowing through the flow regulation valve, the cooling water being a liquid, and the load factor during an operation, regulating an opening degree of the flow regulation valve such that a sum of the first and second flow rates is a predetermined circulation flow rate.
 19. The operation method of a centrifugal chiller according to claim 17, wherein the refrigerant is a low-pressure refrigerant whose pressure in normal use is less than 0.2 MPa. 